1. Field of Invention
The present invention relates generally to a two piece cable tie with a preformed bent metal locking device.
2. Description of Related Art
Plastic cable ties having metal locking device inserts are well known in the art. Examples of such include U.S. Pat. No. 3,457,598 to Mariani and U.S. Pat. No. 5,517,727 to Bernard et al.
Cable ties of this type include a metal locking device partially embedded at an angle within a strap accepting channel of a cable tie head. The metal locking device is situated at an angle that allows insertion of a cable tie strap in an insertion direction, but allows for engagement of the locking device with the strap when it is pulled in a removing direction to prevent removal. The metal locking device of such conventional cable ties is in the form of a cantilevered beam that is fixed at one end and extends into the strap accepting channel at the free end.
Most of such cable ties are formed using a straight section of metal as the locking device. To achieve the desired angular relationship relative to a strap insertion channel, the straight locking device must be inserted into a metal locking device receiving cavity at an angle. However, clearances to achieve such mounting are difficult due to the minimal space provided by the strap accepting channel. Moreover, achieving a proper angular relationship within such tight constraints can be difficult to achieve.
An alternative solution can be found in U.S. Pat. No. 5,815,891 which provides a straight metal locking barb that is inserted into a locking barb receiving cavity parallel to the strap accepting channel. Then, once the locking barb has been mounted into a mounting surface of the head, the locking barb is mechanically bent to have an obtuse angle so that a sharpened free end of the locking barb is within the strap accepting channel. However, there are several difficulties with such a method of installation. First, the size of the cavity and locking barb are quite small. Achieving a desired bend angle within such constraints would be nearly impossible. Second, to achieve a desired bend angle requires overbending. That is the metal must be bent by a certain extra angular amount than a desired angle because upon release of the bending force the metal will slightly relax and elastically straighten out by a certain degree. Due to the provision of a stop member in the 891 patent bending may not occur beyond an angle where the locking barb abuts the stop member without possible damage to the stop member. However, due to the elasticity of the metal upon bending, the free end of the locking barb will straighten out by a certain amount after the bend. This leaves the free end of the locking barb located an undesired angular distance away from the stop member.
Another patent U.S. Pat. No. 5,193,251 provides a different type of cable tie with a pair of bent locking barbs. The cable tie of the 251xe2x80x2 patent is a four-piece tie that utilizes a pair of barbs within a locking head having a pair of strap passageways that allow passage of a non-integral strap for surrounding a bundle or the like. However, the patent is silent as to how the barbs are formed. The locking head does not appear to specifically include a stop member. However, to the extent that a stop member is provided, the locking barbs are spaced by a certain substantial distance above the member so as to be freely pivotal or bendable by a certain degree. The 891 patent discusses the 251 patent briefly and alleges that the barbs in the 251 patent are prebent. Nonetheless, there is no specific teaching of how such prebending could be performed, the resulting structure or any advantages to prebending. If anything, the 891 patent""s teaching of bending after insertion of the locking barb into the cavity teaches against use of prebent barbs.
There is a need for a two piece cable tie with an improved locking device structure that can be readily inserted into a cable tie locking head.
There also is a need for a two piece cable tie with a bent metal locking device that has a predetermined bend angle and is precisely located within a locking device receiving cavity.
There also is a need for a low profile two piece cable tie having a prebent metal locking device provided in a cable locking head that is oriented with a strap accepting channel parallel to a strap attachment axis.
It is an object of the invention to provide a two piece cable tie with a locking device that can be assembled more readily.
It is another object of the invention to provide a two piece cable tie with a bent locking device that can be bent at a predetermined bend angle and precisely located within a locking device receiving cavity.
It is another object of the invention to provide a cable tie having a bent locking device provided in a cable tie locking head that is oriented with a strap accepting channel parallel to a strap attachment axis.
The above and other objects are achieved by a cable tie comprising: a strap including a first end and a free end; a locking head including a strap accepting channel in the head that divides the locking head into a first part and a second part, the strap accepting channel having a strap entry end and a strap exit end on opposite ends of a strap accepting channel axis the first part of the locking head being secured to the first end of the strap along a strap attachment axis, the locking head further including a metal locking device receiving cavity adjacent to and open toward the strap exit end of the locking head and an extending wall located between the receiving cavity and the strap accepting channel; and a prebent metal locking device mounted within the metal locking device receiving cavity by having a fixed end mounted to a support slot of the end wall of the locking head and oriented substantially parallel to the strap accepting channel axis, the metal locking device further including a free end angled at an acute angle relative to the strap accepting channel axis and extending into the strap accepting channel, the free end substantially resting upon a fulcrum point of the extending wall.
The invention also provides a method of making a cable tie comprising the steps of: molding a cable tie strap with a first end and a free end and a locking head secured to the first end of the strap, the locking head including a strap accepting channel having a strap entry end and a strap exit end aligned along a strap accepting channel axis, the strap accepting channel dividing the locking head into a first part and a second part with the first end of the strap being secured to the first part, the locking head further including a metal locking device receiving cavity adjacent to and open toward the strap exit end of the locking head and an extending wall located between the receiving cavity and the strap accepting channel: forming a metal locking device, the metal locking device being formed with a fixed end and a free end that is angled at a predetermined acute angle relative to the fixed end, the free end also having a predefined total free length TFL; and inserting the metal locking device into the metal locking device receiving cavity with the fixed end being substantially parallel to the strap accepting channel axis until the fixed end is securely mounted in a slot of the locking head and the free end has a predefined overlap length OL that extends from the extending wall into the strap accepting channel.